Generally, an electric oven is a utensil for keeping a temperature in a cavity suitably by heating of a heating wire. In particular, a plurality of heaters are prepared at upper, lower and side surfaces in the cavity so that the inside of the cavity may be three-dimensionally heated. Furthermore, a magnetron may be additionally installed to one side of the inner circumference of the cavity so that foods are cooked by electronic waves generated by the magnetron.
In the electric oven, the most important thing is to keep a temperature in the cavity at a desired level. In order to keep a suitable temperature in the cavity as mentioned above, a plurality of heaters are generally repeatedly turned on and off. For example, if a current temperature in the cavity is not higher than a set temperature, the heaters are turned on/off at a set interval so that the inside of the cavity is heated up to the set temperature. On the while, if a current temperature is higher than the set temperature, the heaters are turned off, not to give heat into the cavity.
However, since the conventional heat controlling method controls the oven by turning off the heaters if a temperature in the cavity is high, but turning on/off the heaters at a set interval if the temperature in the cavity is low, there may be caused local overheating. In addition, since the electricity is instantly turned on/off, a breaker switch may be turned off.
Moreover, since the heaters are operated at a predetermined fixed period, it is impossible to accurately satisfy an optimal operating condition suitable for various circumstances. In more detail, as an example, if a temperature in the cavity is approaching a set temperature, a heater with small heating capacity is generally operated, but even in this case, the heating capacity should be controlled in consideration of an amount of the foods received in the cavity. However, since the heaters operated at a given interval, the temperature in the cavity may be continuously decreased due to their small capacity when a lot of foods are received in the cavity. On the while, if an amount of foods is small, the heater may be so frequently turned off, thereby probably causing a problem in the circuit of the electric oven or the domestic circuit breaker.